1. Field of the Invention
The present invention relates to a solid-state imaging device, a method of driving a solid-state imaging device, and an imaging apparatus, and more particularly, to a solid-state imaging device, a method of driving a solid-state imaging device, and an imaging apparatus in which an offset is set in a reference signal in analog-to-digital converting of a pixel signal.
2. Description of the Related Art
Solid-state imaging devices such as charge coupled devices (CCD) or complementary metal oxide semiconductors (CMOS) have been used for various applications. The CMOS type solid-state imaging devices suitable for higher-speed imaging have attracted attention and various architectures thereof have been suggested.
Here, in the analog-to-digital conversion in which pixel signals are converted into digital signals in the CMOS type solid-state imaging devices, a double-slope-type column ADC system in which two slope signals as the reference signal are compared with the pixel signals by a comparator is employed (for example, see JP-A-2008-187565 and JP-A-2008-193373).
In the CMOS type solid-state imaging devices employing the double-slope-type column ADC system, the amplitude of a basis signal in an auto-zero period of the reference signal output from the reference signal generating unit, the amplitude of a slope in a P-phase period, the amplitude of a slope in a D-phase period are changed in analog gain adjustment. The analog gain and the amplitudes of the reference signals are in inverse proportion to each other and the ratios of the amplitudes are constant.